Manufacture of files



g Unites ST TES PATENT omea MARTIN A. HOWELL, JR, OF CHICAGO, ILLINOIS.

MANUFACTURE OF FILES.

SPECIFICATION forming part of Letters Patent No. 258,301, dated May 23,188 2, Application filed July 5,1881. (No specimens.)

To all whom it may concern: 7

Be itknown that I, MARTIN A. HOWELL, Jr., a citizen of the UnitedStates, residing at Ohiago, in the county of Cook and State of Illinois,have invented certain new and useful Improvements in the Manufacture ofFiles and I do hereby declare that the following is a full, clear, andexact description of the invention, which will enable others skilled inthe art to Which it appertains to make and use the same.

Heretofore files have been made from barsteel from steel cast incrucibles and forged into bars, in order to give greater tenacity to themetal, and to give a greater regularity to the combined carbon in themetal; but, in consequence of the repeated forgings,-l1eatin g, andreheating, much of the carbon is lost by the process, and the surfacewhich should contain the carbon intact, in order to give the greatesthardness to the teeth, is rendered really the weakest, while the excessof labor attendant upon this process of forging of the blanks, and thewaste of material and of f ucl enhance the value to the consumer.

The nature of my invention relates to the employment or use ofdecarburized cast-iron blanks in the manufacture of files, in cuttingand finishing the same while the metal is in the soft decarburizedcondition, and in recarburizing the blanks after surfacing and cutting,in order that no carbon shall be lost by the pro cess, but retainedintact where its presence is most essential for the purposes intended.By this means the original natural or granular character of the metal ispreserved, the particles are not crushed by anyprocess of forging, theaffinity for carbon is greater when heated to the proper degree, and ahardness is secured which can only be given by carbon unimpaired, thusenabling me not only to produce a much cheaper file, but one of fargreater durability and regularity.

I take a medium grade of white or refined iron, charcoal-iron beingpreferred, more particularly Lake Superior iron. I proceed to produce mycastings in the usual way from patterns in sand or flasks of refractorymaterials. When the castings are completed they are cleaned fromanyadhering sand or dirt in a rattle-barrel, when the blanks are placedin flasks or saggers, interlaid with oxides of iron, iron scale, or anymaterial having an affinity for carbon, kept at a red heat until theblanks are properly annealed, when, after gradual cooling, they aretaken out, cleaned, and surfaced upon a grindstone, in order to preparethem fortheprocess of cutting the teeth, which is done in the usual way.The blanks are then placed in air-tight boxes, or boxes which can bekept air-tight by proper luting, interlaid with sifted carbon, animal orvegetable, or in a mixture of carbon and salts, all of which is wellknown, and varied to suit the taste ofthe operator or the character ofthe work intended to be produced, when they are kept at a red heat for atime corresponding to the depth of the carbon required,or the depth ofthe decarburized surface of the soft blank previous to cutting, whenthey are immediately taken from the cascs'and hardened in cold water, orcold water containing one of the forms of soda, in order to hold thecontact of the water to the surface of the red-hot blank while immersed.

An uncertain degree of superficial hardness can be secured, without theuse of the cementation process of embedding the blanks in carbon incases, by heating the blanks to a red heat and coating the surface withthe ferrocyanide or prussiate of potash, salts of ammonia, &c., andplunging the file'in water or other-liquids, all of which is well known;but I prefer the cementation process, as it gives a solid character tothe work, and a durability absolutely requisite in the abrasion of hardmetals.

It will be readily seen by any person versed in manufacture that thegreater expense of refined bar-steel as compared with the castiron, thesaving of fuel, ofwaste, and. largely of labor enables me to produce myblanks at a far cheaper rate than where produced by the wellknownprocesses in use, while the superi ority of the work in tenacity anddurability is overwhelmingly in favor of this process.

I am aware that files have been made of wrought or bar iron by the sameprocess as in common use in the making of steel files, save that theywere hardened in a way somewhat analogous to mine, but of a veryinferiorchar-v acter, being equally expensive as to fuel, labor, and material,save a trifling difference in the latter, but rendered generallyunsalable from the inferior and uncertain character of the hardness, andthe liability of all such closelyforged metals to blister when subjectedto the cementationprocess-a difliculty not encounwhich combines thedecarburization of east- 15 iron blanks for the purpose of softening andcutting, with the subsequent recarburization for the purpose ofhardening and tempering, substantially as set forth.

2. In themanufacture of files, the combined process of surfacing,cutting, recarburizing, and hardening ofdecarburized cast-iron blanks,substantially as and for the purposes set forth.

MARTIN A. HOWELL, JR,

Witnesses W. D. BRADSHAW, QHAs. E. SMITH.

